Millions of users were affected, and thousands took to Twitter on Wednesday and Thursday to complain under the hashtag #facebookdown.
USA prosecutors have launched a criminal investigation into the social network's practice of sharing users' data.
The Menlo Park, California-based company, which gets a vast majority of its revenue from advertising, told Bloomberg that it was still investigating the overall impact "including the possibility of refunds for advertisers".
As for its short-term concerns, Facebook still hasn't publicly stated why it was hit with such a devastating outage in the first place, and it's unclear how it will deal with angry advertisers.
Of the products in the Facebook stable, the most direct competitor to Telegram is the private messaging service WhatsApp. The company said it has fixed the glitch. Will Cathcart will be the new head of WhatsApp.
While the outage continued, The New York Times reported that U.S. prosecutors have launched a criminal investigation into the social network's practice of sharing users' data with companies without letting them know.
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The actress is expected to appear before a federal judge at the District Court in downtown LA later today, per the New York Post . He sat in the courtroom where Huffman had her first appearance and appeared to read legal documents during the proceedings.
The agreements let the companies see users' friends, contact information and other data, sometimes without consent.
Regulators, investigators and elected officials in the USA and elsewhere in the world have already been digging into the data sharing practices of Facebook.
"As people become more reliant on digital services like Facebook, Instagram and Youtube, we are witnessing an ever growing number for problems during outages", Sanders said.
"As we've said before, we are cooperating with investigators and take those probes seriously. We've provided public testimony, answered questions and pledged that we will continue to do so".
These issues arose just a short while after Facebook CEO Mark Zuckerberg announced plans to unite all of Facebook's services closer together in a more cohesive user experience. The company has a large campus of data centers in Prineville.